Jonny spielt auf

Scene 1, glacier (1927 Dresden premiere)

The opera singer Anita is walking in the mountains. Lost, she meets the composer Max, who is admiring a glacier. She recognizes Max and tells him that she sang the title role in one of his operas. Both return together to the mountain hotel. A few days later, and it is clear Max has fallen in love with Anita, but she has to leave for Paris where she is performing in his new opera.

As jazz plays in the foyer of a Paris hotel, a chambermaid, Yvonne, who is in a relationship with the jazz fiddler Jonny, is cleaning the room of the famous Daniello – a concert violinist. Jonny slips into the room, sees Daniello's Amati violin and decides to steal it but is prevented from doing so by Anita's arrival. Wasting no time. Jonny makes a none-too-subtle pass at Anita and they are in a embrace when Daniello shows up. Daniello pulls Jonny off Anita, locks up the valuable violin, and takes Anita to his bedroom. Jonny observes this and, with the help of key he has obtained from Yvonne, steals the violin and hides it in Anita's banjo case.

The next morning Anita leaves Daniello's room to meet with her manager and sign a contract that will take her over to America to sing there. Daniello then discovers his violin is missing, realizes someone has to have had access to his room and summons the hotel manager who sacks Yvonne. Daniello thinks Anita is in some ways involved and decides to take revenge by embarrassing her. He gives Yvonne a ring Anita has just given to him, telling Yvonne to show it to Max and tell him about his and Anita's affair, then he follows Anita. Jonny also is also in pursuit of Anita because she has with her the banjo case containing the priceless violin.

Back in Anita's house in the Alps, Max is asleep, having stayed up all night waiting for Anita. When Anita finally arrives she is hardly affectionate, puts the banjo case on the piano and heads to bed. Shortly after, Yvonne arrives, tells Max about Anita's love life in Paris and shows him the ring. Max storms out to seek solace and calm by beside the glacier.

Meanwhile, Jonny shows up. Yvonne thinks he has come to make up with her while Jonny thinks Yvonne is trying to recover the violin to return it to Daniello. Opening the banjo case and grabbing the violin, Jonny escapes through the window. Now we find Max beside the glacier and contemplating throwing himself into one of its deep crevices but the glacier speaks to Max, advising Max against suicide.

Scene 9, railway station (1927 Dresden premiere)

The sound of Anita's voice, singing one of Max's arias on the radio and broadcast via a hotel loudspeaker floats up to Max and he realizes he must return to Anita. The radio station plays another track, this time of Jonny's jazz band and Daniello, who is also listening to the broadcast while staying in another hotel recognizes the sound of his Amati violin. Realizes who the thief was, Daniello sends a telegram to alert the police. Three policemen pursue Jonny who is trying to flee to America with the violin. One of the policemen finds a railway ticket dropped by Jonny. Max has by chance come to the same railway station and Jonny, observing Max's luggage being deposited on the platform, slips the violin (now in Jonny's battered violin case) among Max's suitcases. The policemen see the violin case, seize it and arrest Max. Anita, who had been summoned by telegram to the station so Max could say goodbye to her face-to-face, arrives but Yvonne and Daniello are also there, and when Daniello tells Anita that Max has been arrested, Anita demands that Yvonne explain to Daniello Max's innocence. In the ensuing confusion Yvonne accidentally pushes Daniello off the platform and he is killed by an incoming train.

Jonny meanwhile knocks out the sleeping driver of the police van, taking his place behind the wheel while Max and the violin case are placed inside the van, and another policemen sits in the passenger seat. The van speeds off but Yvonne has managed to persuade Jonny to help Max so when max asks the driver turn around Jonny pushes the other policemen out of the van, turns the van around and heads back to the station. The train with Anita on board is pulling out of the station when Max jumps into her compartment and Jonny, violin in one hand, can be seen climbing onto the hands of the giant station clock high above the platform. When Jonny starts to play, all the passengers start to dance, then magically transferred to the North Pole, Jonny leads the whole world in dancing ... and all the other characters in the opera urge the audience to join in, too.